A liquid crystal panel included in a liquid crystal display device does not emit light, and thus a backlight device is required as a separate lighting device. The backlight device is arranged behind the liquid crystal panel (i.e., on a side opposite from a display surface side). It includes a chassis having an opening on a liquid crystal panel side, a plurality of LEDs (light emitting diodes) accommodated in the chassis as light sources, and a light guide plate and the like that efficiently guides light emitted from the LEDs to the liquid crystal panel.
In such a backlight device, brightness may be remarkably different in a portion in which the LEDs are arranged and a portion in which no LED is arranged. Therefore, the point light emitted from each LED is converted to planer light by an optical member such as the light guide plate to obtain uniform illumination light. A generally known method for obtaining uniform illumination is disclosed in Patent Document 1.    [Patent Document 1] Japanese Unexamined Patent Publication No. 2007-178836